Radio receiving system



May 11 1926.

E. w. KELLOGG RADIO RECEIVING syswsm Fil ed Oct. 29. 1924 Pi .2. M"

I g] lag I. 6 /4 b 4 W /2 Fig.3 M: l, f 7 x Inventor: EdwardWKeHogg,

Patented May ll, 1926..

FATE? EDWARD W. KELLOGG, 0F SGEEN'E C'IADY, NEV] YORK, ASSIGNOR TOGENERAL ELEC- 'lIR/I'G COMPANY, A COBPORATIDN 015 NEW YORK,

RADIO RECEIVING SYSTEM.

Application .filecl October 29, 1924.

My present invention relates to radio receiving systems and moreparticularly to an arrangement of antennm which is especially adaptedfor radio reception. My present application is a continuation in part ofmy copending application, Serial No. 552,868, filed April 15, 1922.

In my U. S. Patent, 1,487,389 issued March 18, 1924 I have described andclaimed a unidirectional antennae system made up of two horizontalconductors and have described and claimed a means whereby the antennaconductors may be employed as a transmission line for carrying signalingcurrents from a point in the antennae where they are most favorable forreception to a distant point along the length of the antennae Where thereceiving station may be more conveniently located. I have alsodescribed and claimed in that patent certain methods for neutralizingthe effect of undesired cur rents in the receiving apparatus.

The object of my present invention is to provide a receiving systemwhereby the results described in my prior patent may be brought about ina somewhat simpler manner.

The improvements which I wish to cover in thepresent applicationconsists principally in apparatus and connectionsfor producingreflections ofmurrent, over the con.- doctors of the receiving antennain such a way that in some cases the need for current transformers maybe eliminated. I have also provided simple means for adjusting thereflections in order to secure the most satisfactory reception. 7 v

The novel-features which I believe'to be characteristic of my inventionare set forth with particularity in'the appended claims, My inventionitself, however, both as to its organization and method of operationwill bestbe understood by reference to the'following description takenin connection with the'accompanying drawing in which Figs. 1 2 and 3show diagrammatically three different circuitorganizations whereby myinvention may be carried into effect.

In each figure of the drawing'I have indicated a long antennamade up oftwo parallel, horizontal conductors 1 and'2', ground connections areprovided at the ends 3 and 4 of the antenna. In Fig. 1 the groundconnection at- 3 is made tlHOUgl'l a resistance 5 having a resistancesubstantially equal to the Serial No. 746,648.

surge impedance of the antenna to prevent undesired reflections backover the length of the conductors. In the arrangement shown in Fig. 1 itis assumed that it is desired to receive signaling waves traveling alongthe antenna through the ether from the end 3 toward the end 4 but thatit is desired to locate the receiver 6 at or near the end 3 of theantennae. In order to be-able to locate the receiving station at the end3 of the antennas in this case it is necessary to provide means fortransmitting the desired signaling currents received upon the an tenneewhich are strongest at the end 4 back toward the end 3. In my priorpatent above referred to I have accomplished this by means of atransformer located at the end 4. In the present case, however, thedesired effect may be obtained byo'pen circuiting the end of conductor 1at end 4 of the antenna and directly grounding conductor 2. The resultof this arrangement is to produce an open circuit reflection back alongthe length of conductor 1 which is superimposed upon the current wavebuilt up on the antenna by,

the signal in such phase and magnitude as to produce zero current at theend 4 of conductor 1. At the same time a short circuit reflection isproduced in conductor 2 which in effect practically doubles the Icurrent flowing in that conductor. Thus'the opening of conductor 1 andthe grounding of conductor 2 produces an effect at the end4 of theantenna exactly equivalent to the efiect obtained by the use of atransformer as'described in my prior patent and the effect upon thereceiver 6 will also be the same as though a' transformer had beenemployedat the end 4.

The winding 7 of transformer 8 in Fig. 1 is not affected by currentsflowing in the same direction in the two conductors of the antenna, butis affected'by currents which flow in opposite directions in the twoconductors. The signal wavesbuilt up on the antennae flow in'the samedirection through both conductors, but the waves reflected from the end4 in the manner described in my present invention, flow in oppositedirections in conductors 1 and 2 andth'erefore affect the receivingset 6through the transformer 8.

By reason of the resistance in the ground connection at 4 there iuay bea loss ofenerg'y in the short circuit reflection and the reflectcdcurrent in conductor 2 will then be less than that in conductor 1. Thisunbalance may in some cases be detrimental as will be more fullydescribed later. This difficulty may be overcome by the provision of aleak resistance 9 which may be connected between the end of conductor 1and ground by means of a switch 10. The resistance of this leak shouldbe approximately such that R zZzZzR in which proportion B is theresistance of the leak 10, K the resistance of the ground and Z thesurge impedance of one conductor with ground return.

In my prior patent referred to above I have also indicated ways in whicha portion of the currents which would flow through the ground connectionat end of the antenna, in the case just described, may be utilized forneutralizing the effects of disturbing currents which are found at theopposite end of the antenna and are transformed and transmitted over theline back to the receiver. In practice it is generally found desirableto make use of a neutralization of the nature described in my patentreferred to and when such a system is employed the detrimental effectsof an unbalance such as that referred to in the previous paragraphbecome more apparent.

In Fig. 2 I have indicated diagrammatically a receiving system in whichmeans for securing such neutralization is provided. This system is soarranged that the currents in circuits 11 and 12 can be combined in anydesired relative intensities and phases and supplied to the receiver 6.Assume that the desired signal is traveling in the direction 3-4: andthat some disturbance which, for convenience may be called static, iscoming from the opposite direction. The current indicated by the arrowmarked I which is transmitted back to end 3 by means of the transformeris principally signal current with a residual of static while thecurrent- I is principally static. A small. fraction of the energy of Iis supplied to the receiver through circuit 12 in such phase andintensity as to balance out the residual static in I.

If now the transformer 13 is imperfect and instead of transforming allof the power brought to it by I reflects part of the waves back over thetwo wires in multiple the reflected component will then appear at 3mixed with I. In attempting to make a balance for minimum static it nowbecomes necessary to use a mixture of I and I to balance the residualstatic in I and when the static is balanced it may frequently happenthat the I component in circuit 12 has subtracted in the receiver fromthe I brought in through circuit 11 thus weakening the useful signal.Consequently it has been found in practice that the best balances areobtained when one of the components has as much signal and as little static as possible and the other as much static and as little signal aspossible.

Reflection at either 3 or a in this case tends to mix the two componentsbefore they reach the receiver where they are available for balancingoperations. It the useful signal comes from the direction -l3 and thestatic or interference from the direction 3 1: it is especiallyimportant to avoid rc fleeting part of I back over the two wires inmultiple. This is because it does more harm to mix unnecessary staticwith signal current before the balancing operation. than to mix somesignal current with the static. lVhen a reflection transformer 13 isused as indicated in Fig. 2 it is desirable to use series and shuntresistances l-it and 15 on the primary side as shown in order that thetotal impedance in the ground connection may be more nearly a pureresistance and may be made more nearly equal to the surge impedance ofthe antenna. This throws away part of the static current I" but there isa large surplus. since only a small fraction of I is required forbalancing purposes. \Yith the resistances 1 1 and 15 omitted it isdifiicult, because of the reactance of the transformer 13, to avoidreflecting a considerable fraction of I back over the antenna wires inmultiple and having it appear mixed with the signal current I.

In Fig. 3 I have indicated a method whereby the result described inconnection vith Fig. 2 may be obtained without the use of the reflectiontransformer 13.

If the impedance or resistance of 16 high compared with the surgeimpedance of one wire and that of 17 is correspondingly low thereflected waves on the two wires will be opposite in phase. If 16 and 17differ only slightly from the surge llllpedance the amount of energysent back on the transmission line will be small, most of the energywhich reaches 1' being absorbed in the resistances. On the otl'ier handil it is desired to transmit as much power as possible back over thetransmission line, 17 should be zero and 16 should be an infiniteresistance or open circuit.

If the waves built up on the antenna conductors are reflected at the end1 the r flected waves may in any case be resolved into two parts. oneconsisting of a pair of waves identical in phase and magnitude on thetwo conductors and the otber eonsisting of a pair of equal and oppositewaves on the two conductors. The former representv power reflected backover the antenna which will appear in circuit 12 while the latter may bethought of as transformed waves. If we wish to avoid reflecting any ofthe power back over the antennae, the reflections on the wiresindividually must be equal and opposite. This condition may be met withlln various combinations of impedances 16 and 17 some of which willabsorb little power and transform most of it while others will absorbmost of the power and transform little.

What I claim as new and desire to secure by Letters Patent of the UnitedStates, 1s:-

1. The combination in a radio receiving system of a long horizontalantenna made upof two parallel conductors, means at one end of saidantenna for producing reflections of different phases in the twoconductors and means for adjusting the reflections in one of saidconductors.

2. The combination in a radio receiving system of a long horizontalantenna made up of two parallel conductors, means at one end of saidantenna for producing reflections of different phases in the twoconductors and means for adjusting the reflections in both of saidconductors.

3. The combination in radio receiving system of a long horizontalantenna made up of two parallel conductors, both of said conductorsbeing grounded at one end and both of said conductors being grounded atanother point through individual resistances of difi erent values.

4. The combination in a radio receiving system of a long horizontalantenna made up of two parallel conductors, receiving apparatus locatedat one point along said antenna, means at another point in said antennafor producing reflections of different phase in the two conductors andmeans for adjusting the reflections in one of said conductors.

5. The combination in a radio receiving system of a long horizontalantenna made up of two parallel conductors, receiving apparatus locatedat one point along said antenna, means at another point in said antennafor producing reflections of differ ent phase in the two conductors andmeans for adjusting the reflections in both or" said L:

conductors.

6. The combination in a radio receiving system of a long horizontalantenna made up of two parallel conductors, receiving apparatus locatedat one point along said antenna, means at another point in said antennafor transmitting energy over the two conductors to the receivingapparatus comprising means for producing reflections of different phasein the two conductors and means for adjusting the amount ofenergyreflected and the phase of the reflections in the two conductors.

In witness whereof, I have hereunto set my hand this 28th day ofOctober, 1924.

EDWARD W. KELLOGG.

